Streptococcus mutans & other streptococci


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Streptococcus mutans & other streptococci

  1. 1. STREPTOCOCCUS MUTANS Dr. Ali Yaldrum Faculty of Dentistry, SEGi University.
  2. 2. LEARNING OBJECTIVES At the end of this session, the student should be able to:1.Describe what are Streptococci Organisms2.Classification of Streptococci Organisms3.Describe role played by Streptococcus mutans in health and disease
  3. 3. 1. GENERAL PROPERTIES• Catalase negative• Gram +ve• Spherical or Oval Cocci• Appears in pairs or chains• 0.7 to 0.9 um in diameter• causes a wide variety of diseases (fig. 1)
  4. 4. 2. PATHOGENICITYPathogenic Streptococcus produces several extra cellularsubstances that contribute to their pathogenicity
  5. 5. 2. PATHOGENICITY1. products that destroy the phagocytic cells & ingest them2. produces enzymes that digest the connective tissue resulting in extensive tissue destruction3. can also lyse “Fibrin”
  6. 6. pneumonia endocarditiscariesmeningitis necrotizing fasciitis (see fig 2&3) (fig 1)
  7. 7. facial cellulitis which progressed relentlessly with necrosis (fig 2)
  8. 8. (fig 3)
  9. 9. 4. CULTURE• Grow well on blood agar• There are 3 types of hemolytic reactions produced on blood agar (fig 4 & 5) 1. α -hemolysis 2. β-hemolysis 3. γ-hemolysis
  10. 10. β-hemolysis wide clear translucent zoneof complete hemolysis around α -hemolysis the colony narrow zone of partial hemolysis γ-hemolysis: no hemolysis occurs T YP ES OF HEMOLY T IC REAC T IONS (F IG 4)
  11. 11. shorter arrow: α hemolysis longer arrow: β-hemolysis T YP ES OF HEMOLY T IC REAC T IONS (F IG 5)
  12. 12. 3. SEROLOGY• Surface Carbohydrate antigens are related to their virulence• Hence serogrouping termed Lancefield grouping is useful in identification of the more virulent β-hemolytic species• 20 Lancefield groups are recognized
  13. 13. MUTANS GROUP
  14. 14. • originally isolated from human teeth by Clark in 1924• in 1960 caries were induced experimentally in animals, artificially infected with strains resembling S.mutans• cells can loose their coccal morphology and appear as cocco-bacilli
  15. 15. • 9 serotypes have been identified (a-h & k)• Human isolates are : c,e f and k• S.mutans have been implicated as the primary pathogen in : 1.enamel caries in children & young adults 2.root surface caries in elderly
  16. 16. • occupy hard non-shedding surfaces i.e teeth or dentures• Regularly isolated from dental plaque at carious site, but low prevalence on sound enamel• opportunistic pathogens (isolated from cases of infective endocarditis)• communicate with other mutans
  17. 17. • cell wall carbohydrate antigen (I/II)• lipoteichoic acid• lipoproteins• cell wall associated protein
  18. 18. contribute to characteristic colonial morphology Extracellular Polysaccharides (glucan, mutan, fructan) glucosyl and fructosyltransferase Streptococcus mutans excess sugar Intracellular Polysaccharides (glucan, mutan, fructan)act as carbohydrate reserve, used to produce acid in absence of available sugar
  19. 19. Salivarius group
  20. 20. This group consists of two bacterias1. S. salivarius2. S. vestibularis
  21. 21. • salivarius prefer mucosal surface especially the tongue• produce unusual quantity of extracellular fructan• rarely isolated from diseased sites
  22. 22. • S. vestibularis prefers the vestibular mucosa• no extracellular polysaccharide production• produces ‘urease’ leading to rise in local pH and hydrogen peroxide
  23. 23. Anginosus group
  24. 24. The group is differentiated into• S. constellatus• S. intermedius• S. anginosus
  25. 25. • readily isolated from dental plaque & from mucosal surface• cause serious, purulent diseases• commonly found in abscess of internal organs• no strain produces polysaccharide from sucrose
  26. 26. Mitis group
  27. 27. This group consists of• S. sanguinis• S. gordonii• S. mitis• S. oralis
  28. 28. • Early colonizers of tooth• produce soluble and insoluble glucans from sucrose• contribute to plaque formation• ammonia generation from arginine
  29. 29. • S. sanguinis produces a protease that can cleave sIgA• S. gordonii can bind with salivary amylase enabling the breakdown of starch
  30. 30. References1. Philip D. Marsh, Michael V Martin, “The Resident Oral Microflora” in Oral Microbiology, 5th Edition,Churchil Livingstone, 2009, pp 25-35